PURPOSE: To provide a cathode structure of an X-ray tube which ensures that components of a convergence electrode are easy to fabricate and a cathode filament is assembled easily.

CONSTITUTION: Those mating surfaces 14, 15, 16 of a cup-shaped convergence electrode 11 which confront an anode target 21 are made in a horizontal plane, which is provided with a plurality of converging grooves 12, 13 whose processing directions consist only of ones perpendicular to one another. In these converging grooves 12, 13, cathode filaments 17, 18 are installed, at least one of which is located in eccentricity from the groove center across its width toward the end.